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Show Table 1. Properties of Highvale Coal Coal Type: Heating Value Proximate Analysis Moisture Ash Volatiles Fixed Carbon Total Ultimate Analysis Carbon Hydrogen Nitrogen Sulphur Ash Oxygen Total Highvale coal 10361 Btu/lb W t % (dry) - 17.25 33.55 49.2 100 63.01 3.87 0.86 0.24 17.25 14.77 100 (4 seam blend) 24.1 MJ/kg W t % (wet basis) 10.5 15.44 30.03 44.03 100 56.39 3.46 0.77 0.21 15.44 13.22 89.5 Several experimental runs in an air and 02/C02 combustion mode were undertaken as part of the newly constructed pilot plant commissioning trials. These trials were very successful in demonstrating the safe and reliable performance of all process equipment, controls and the data acquisition system. Some optimisation of the burner design was also undertaken in the shake down trials to ensure stable coal and natural gas combustion in feed gas mixtures of varying C 0 2 and 0 2 compositions and air. For the coal trials proper, a matrix of 4 combustion runs was undertaken with the Highvale coal. These tests included a baseline run on air and three other runs with 21/79, 28/72 and 35/65 per cent by volume of oxygen/carbon dioxide mixtures. The overall process configuration adopted in the tests involved the use of the indirect coal system to deliver fuel to the combustor. Ash particulates were removed during the runs from the bottom of the combustor, in the cyclone and in the bag filter unit. All other flue gas treatment units shown in the process schematic of Figure 1 were bypassed. To prevent excess heat let down from the flue gas at the lower coal firing rate, the glycol boiler was also converted from a triple pass to a single pass mode of cooling. A typical run undertaken during the trials involved a 3-4 h warm up period firing natural gas air. Once the combustor had warmed up to maintain its steady state refractory temperatures, the unit was slowly switched to pulverised coal firing with simultaneous reduction of the natural gas input. In the case of trials undertaken with the 02/C02 mixtures, the unit was first shut down from natural gas and air operation and restarted on a natural gas-02/C02 mode of operation. From 6 |